1. Field of the Invention
The present invention relates to a method to derive anatomical and/or pathological structures using digital imaging data by non-invasive imaging technologies such as computer tomography (CT) or magnetic resonance imaging (MRI) as well as optical, ultrasound or laser-based scanners. These techniques involve different key areas: To start with, one key area is the reproduction of individual body surfaces (forms) for radiotherapy treatment planning, follow-up and functional imaging. A further key area is the reprint of an anatomical structure or an organ of the human body for preoperative planning, surgery support and guidance, teaching tools for validation of bioengineering computed simulation and prosthesis generation or manufacturing, respectively.
2. Description of the Background Art
The problem at the moment is a manual production and adaption of masks for radiotherapeutic treatment planning. Theses processes are quite time consuming and not very accurate in fitting to the individual patient's body geometry.
In radiation therapy, tumorous tissue is treated with high-energy beams. The application has to be exactly controlled in order to deliver the dose to the entire tumor and to minimize damage to neighboring healthy tissue. Since most of the radiation therapy is performed by an external radiation therapy device such as a linear accelerator which produces high energy X-rays, healthy tissue usually is affected by radiation as well. Therefore, planning procedures are used to calculate the dosage to be delivered to the tumor and describe as well its dosage to normal tissue. In order to minimize irradiation of healthy tissue and to maximize the amount of dose delivered to the tumor, several angulated radiation beams converging to the tumor site are used. To achieve this, an exact reproducible and stable positioning of the body part affected is of utmost importance.
Also the performance of a stereotactic procedure or an operation requires exact fixation and positioning of the relevant body part in order to localize and target the region of interest.
One method of fixating a body part is to attach fixation rings, e.g. to the skull, which require the attachment of sharpened screws to the bone of the patient. EP 1 227 768 B1 gives an example for a method of designing customizable fixture for patient positioning. According to this disclosure, a method of designing a customized positioning fixture for positioning a body in relation to a medical apparatus comprises the following steps:
First, determination of body mounting data from a scanned image characterizing positions of a plurality of mounting devices on the body is accomplished. This mounting data is used to compute a digital model of the positioning fixture that characterizes a shape of the positioning fixture such that the shape includes a first plurality of mounting structures for meeting with the mounting device on the body and a second plurality of mounting structures for attaching the positioning fixture to the medical apparatus to hold the body in a predetermined position relative to the medical apparatus.
Another frequently used procedure is to plaster a cast around a body part with plastic material. However, this method comes along with several disadvantages. One of them worth mentioning is the duration of winding the plastic cast and a hardening time of about 20 minutes. During this period of time, the patient cannot move, the plaster is warming up and the plaster cannot be removed very quickly. Also an opening of the mask is quite uncomfortable for the patient since the plaster has to be cut open after the mask has adopted a sufficient stability while it is still attached to the patient. Therefore, this method is extremely unpleasant for patients with claustrophobia or young children. At present, sparing out foramina for e.g. eyes, ears or the nose is not possible during the production of the masks.
U.S. Pat. No. 6,459,927 is related to a method for positioning a body in relation to a medical apparatus using a customized positioning fixture comprising: providing a 3-D scanned image of the body; determining from the scanned image of the body mounting data that characterizes positions of a plurality of mounting location on the body; using the mounting data computing a digital model of the positioning fixture such that the shape includes a first plurality of mounting structures that mate with the mounting locations on the body, and a second plurality of mounting structures for attaching the positioning fixture to the medical apparatus; fabricating the positioning fixture according to the digital model; fixing the body to the medical apparatus in a predetermined position of the body relative to the medical apparatus, including mating different plurality of mounting structures with the mounting locations on the body and attaching the positioning fixture to the medical apparatus using the second plurality of mounting structures.
US 2005/0075649 A1 is related to a frameless stereo active guidance of image-based medical procedures. A device for guiding medical procedures is disclosed, which comprises at least subject-specific article comprising at least one reference contour dimensioned to follow a contour of an exterior surface portion of a subject to be treated. The at least one subject-specific article is rigidly attachable to the surface portion, wherein the subject-specific articles provides a customized spatial reference for alignment of a preplanned medical procedure to one or more target regions of the subject. The at least one subject-specific article is to be placed on the subject and a medical procedure is performed on the target region, guided at least in part by the subject-specific article.
WO 2004/110309 A2 is related to a computer-aided design of skeletal implants. A computer-aided design method for producing an implant for a patient prior to operation comprises the steps of generating data with a non-invasive 3-D (3-dimensional) scan of the patient's defect site that digitally represents the area that will receive the implant. Designing and validating an implant on a computer based on digital data generated from a volume image of the patient is performed. Still further, the implant is fabricated based solely on the implant design data generated on computer. Still further, the step of designing an implant based on the data generated from the 3-D scan of a patient is including the step of constructing a surface image representing a patient's defect site from 3-D volume images. The step of generating data includes defining a contour, describing the external boundary of the patient's defect site to receive the implant on the surface image representing a patient's defect site that is derived from the 3-D volume images in an accurate 3-D space.
U.S. Pat. No. 6,310,355 B1 is related to a lightweight radiation shield system. A shield is disclosed for attenuating the flux of electromagnetic radiation from an article. The shield comprises a flexible matrix comprising a film including a radiation attenuating material, the matrix including at least one space within the matrix. The at least one space reduces the weight of the shield without appreciably reducing the attenuating characteristics of the shield.
WO 01/64106 A1 is related to animation technology. A method is disclosed for producing 3-dimensional visualizations of digital representations of cross-sectional slices of a vertebrate animal or human body part and includes the following steps: A first ordered series of slices of a portion of the body part in a first position is obtained. One or more filters are applied to each of the digital representations of the first ordered series of slices to identify the skeletal portions of the body part. The first filtered series is converted into a 3-dimensional representation of the skeleton of the body part in the first position. A second ordered series of slices of the portion of the body part in a second position different to the first position is obtained. One or more filters are applied to each of the digital representations of the second ordered series of slices to identify the skeletal portions of the body part. The second filtered series is converted into 3-dimensional representation of the skeleton of the body part in the second position and the 3-dimensional representations are combined to form a step frame animation having as many steps as there are ordered series of slices.
The publication “Deformable and rigid registration of MRI and microPET images for photodynamic therapy of cancer in mice”, pages 753-760 in Medical Physics, AIP, Melville, N.Y., US, vol. 33, 3, 23 Feb. 2006, ISSN: 0094-2405 discloses an investigation of imaging techniques to study the tumor response to photodynamic therapy. Positron emission tomography provides physiological and functional information. High-resolution magnetic resonance imaging provides anatomical and morphological changes. Image registration can combine MRI and PET images for improved tumor monitoring. In high resolution MRI and microPET F-flourodeoxyglucose images from C3H mice with RIF-1 tumors were treated with Pc 4-based photodynamic therapy. For registration of the whole mouse body, an automatic three-dimensional, normalized mutual information algorithm is used. For registration of tumor a whole body registration has been developed performing slice-by-slice review of both image volumes. Manually segmented feature organs such as the left and right kidneys and the bladder are present in each slice, being computed and the distance between corresponding centroids has been computed. The distance between corresponding centroids of organs was found to be 1.5+−0.4 mm, corresponding to about 2 pixels of microPET images. The mean volume overlap ratios for tumors were 94.7% and 86.3% for the deformable and rigid registration methods, respectively.